You can't keep a good Dell down. After having paid the price two years ago for surrendering its leadership position, it's now clearly rejoining the battle with HP and is inching its way back toward market leadership, according to iSuppli.

It's fair to say that the resurgence of Hewlett-Packard under the leadership of CEO Mark Hurd has been one of the more incredible success stories in the emerging annals of 21st century American business. There were other prospective leaders who could have taken the helm when Hurd did, who might not have led the company away from what seemed certain catastrophe.

But now it appears the battle may be joined, as new sales data from hardware analysis firm iSuppli indicates that, at least between April and June of this year, HP wasn't the fastest car in the race. Its pace slowed a bit -- not a lot, but measurably -- while Dell turned it up to "full rich."

With the onset of the global economic crisis not having yet hit the country in Q2, Dell's worldwide PC unit shipments grew to over 11.2 million units -- 21% more than Dell shipped in Q2 of 2007. HP led the way for the second quarter, however, as it has since the third quarter of 2006, with just under 13.4 million units shipped worldwide, a growth rate of 19.6% annually.

That's still an amazing rate of growth by any measure, but that's down from the first quarter by 3.7%. Dell's growth accelerated in the same period by 1%.

The change-up helped Dell recapture some badly needed market share, gaining 0.7% of global shipments over the previous quarter and 0.9% over Q2 2007, to 16%. HP gained a fraction of market share too: just 0.3% over the previous quarter, to 19.1%.

Analysts at iSuppli credit Dell's repairing its relationships with its retail and channel sellers (it didn't used to sell retail at all, if you'll recall), as well as having overtaken Acer in notebook shipments, reclaiming the #2 spot there. That's actually quite amazing, since it was Acer that was banking its entire worldwide expansion program on the success of new models, especially in the Middle East markets where it has such success.

So if HP and Dell both gained, who lost? In a quarter marked by 14% overall shipment growth -- two percent more than was generally predicted, and certainly extremely healthy by any measure -- the answer is..."Other." Everyone else other than the world's top PC producers dropped a point and a half of collective market share in just one quarter, and 2.2% in one year's time. Acer -- iSuppli's #3 producer, which now incorporates Packard Bell, Gateway, and eMachines brands as well -- was the only market share loser in the top five in Q2, dropping just 0.1% over the previous quarter to 9.5%, shipping 6.65 million units worldwide.

Number four Lenovo had the slowest growth of the top five, with shipments up 14.4% annually to 5.57 million -- still above the global average rate of growth. Toshiba, which unveiled several new notebook models over the spring, surged 23.9% in unit sales to reach 3.18 million.

Any hit to PC shipments on account of the global financial crisis will probably be recorded at the tail end of Q3, and those numbers may probably be tallied and assessed as soon as late November.